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Explore  /  MGF / PEG-MGF (Mechano Growth Factor, IGF-1Ec)
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MGF / PEG-MGF (Mechano Growth Factor, IGF-1Ec)

D
lead outcome
Satellite-cell (muscle stem-cell) activation…
grades vary by outcome ↓
Peptide⚠ WADA-banned
also called — MGF · Mechano Growth Factor · IGF-1Ec (human; IGF-1Eb in rodents) · the IGF-1 E-peptide (Ec) · PEG-MGF / PEGylated MGF (the long-acting form). INCI: none
muscle growth / repairsatellite-cell (stem-cell) activationtissue repair(IGF-1 axis, early proliferative phase)

The "first responder" of muscle repair — elegant splice-variant biology, almost entirely preclinical. Three points define this entry: (1) it's a genuinely distinct piece of biology — an IGF-1 splice variant whose unique E-peptide activates muscle stem (satellite) cells, a different job from ordinary

In brief

MGF (Mechano Growth Factor, IGF-1Ec) is a splice variant of IGF-1 produced locally in muscle in response to mechanical stress or damage. Its distinctive part is a 24-amino-acid E-peptide that acts as an early "first responder" repair signal — it wakes up quiescent satellite cells (muscle stem cells) and makes them proliferate, a job the ordinary circulating IGF-1 doesn't do well. In the natural repair cascade, this MGF pulse comes first (within hours), expanding the stem-cell pool, and is followed by a switch to IGF-1Ea, which drives the actual fiber growth. The biology is elegant and real — but it's overwhelmingly preclinical. Native MGF has an extremely short half-life (~5-7 minutes) by design (it's meant to be a local, transient signal), which is why the gray market sells PEG-MGF (PEGylated, longer-acting) — a form that carries batch-to-batch inconsistency and still lacks meaningful human trials. Add no long-term safety data on artificially activating muscle stem cells, and the honest read is: interesting mechanism, minimal human proof.

Legal standing, by region
European Union
Not FDA-approved (gray-market)

not approved anywhere; investigational research peptide. Not a cosmetic; no compounding pathway.

⚠ WADA-prohibited in sportSport as an IGF-1/growth-factor agent, it falls in WADA-prohibited growth-factor territory.
Evidence, by outcome

An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.

OutcomeEvidence base · effectGrade
Satellite-cell (muscle stem-cell) activation / proliferation
Genuinely distinct, reproducible preclinical biology — but not demonstrated as a human therapy
Well-characterised in cell/animal models — MGF E-peptide activates quiescent satellite cells where mature IGF-1 barely does
D
Muscle repair / hypertrophy (the marketed use)
Very limited human data; no controlled human hypertrophy/repair trials establishing efficacy
Animal / model data on the MGF→IGF-1Ea repair cascade
F
Aged-muscle / regeneration
Interesting rationale (maybe why older muscle repairs slower) — but human interventional data absent
Observation: aged muscle shows a blunted MGF response to loading vs young
F
PEG-MGF as a practical agent
Solves the half-life problem mechanically, but subcutaneous kinetics not formally characterised, and unregulated PEG products vary widely batch-to-batch
PK: PEGylation extends half-life from ~minutes to ~hours/≈24 h
Safety
Injection-site pain/swelling common; no long-term data on chronically/artificially activating muscle stem cells; theoretical concerns (scar tissue, unregulated growth signalling) unquantified
Little formal human data

Identity MGF is a splice variant of the IGF-1 gene (chromosome 12q23). The IGF-1 gene splices exons 4-6 into several isoforms that share the same mature IGF-1 sequence but differ in a C-terminal "E-peptide." MGF's distinguishing feature is its unique 24-amino-acid E-peptide (from a reading-frame shift in exon 5), which has biological activity of its own, independent of the mature IGF-1 domain. The synthetic "MGF" sold for research is typically just this E-peptide. PEG-MGF attaches polyethylene-glycol chains to it to extend its very short half-life. ## Mechanism (as proposed) the IGF-1 gene produces multiple isoforms by alternative splicing. Two matter for muscle: IGF-1Ea (the liver-derived, circulating, systemic anabolic form — "tonic" growth signal) and IGF-1Ec = MGF (the local, mechano-responsive form). When muscle is loaded or damaged, it transiently makes MGF within hours; MGF's E-peptide then activates satellite cells (muscle stem cells sitting dormant between fibers), driving them to proliferate — critically, without forcing early differentiation, so the stem-cell pool expands first. The muscle then switches to IGF-1Ea, whose mature IGF-1 acts via IGF-1R → PI3K/Akt/mTOR to drive myoblast fusion, protein synthesis and fiber hypertrophy. So MGF is the early proliferative trigger; classic IGF-1 is the later growth executor. MGF biology is therefore not simply "more IGF-1" — the E-peptide works through partly different pathways to achieve a different early outcome (proliferation vs differentiation).

Sources — 5 cited
01Goldspink G, et al. — characterization of MGF/IGF-1Ec as the mechano-responsive IGF-1 splice variant (UCL, mid-1990s onward); E-peptide autonomous activity.
02Reviews of IGF-1 splice isoforms and the MGF→IGF-1Ea repair cascade / satellite-cell activation (Hill & Goldspink and successors).
03PEGylation pharmacology for MGF (half-life extension; note un-formalised SC kinetics and batch variability in unregulated products).
04Observations of blunted MGF response in aged skeletal muscle after loading/injury.
05(Note: as of 2026, human interventional efficacy/safety data for exogenous MGF/PEG-MGF remain very limited.)
Review status
Not yet reviewed

A credentialed reviewer (PharmD / PhD / MD) will be named before this entry is finalised. Until then, treat it as a working draft. Last updated July 2026 (watch for any controlled human data — the field is preclinical-heavy; that would move the grades).

Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.

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MGF / PEG-MGF — the mechano-growth-factor muscle peptide: real splice biology, thin human evidence · Vallydia